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Croix E. Christenson, Jonathan E. Martin, and Zachary J. Handlos

1. Introduction Narrow, rapidly flowing currents of air located near the tropopause are known as jet streams or jets. These jets, often found nearly girdling the globe while exhibiting large meridional meanders, are among the most ubiquitous structural characteristics of Earth’s atmosphere and are known to play a substantial role in the production of sensible weather in the midlatitudes. As the primary phenomena at the interface between synoptic-scale weather systems and the large

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Joshua G. Gebauer and Alan Shapiro

1. Introduction Climatological studies have revealed a well-defined maximum in the frequency and intensity of southerly low-level wind maxima over the southern Great Plains ( Bonner 1968 ; Walters et al. 2008 ; Rife et al. 2010 ; Doubler et al. 2015 ). This phenomenon has been named the Great Plains low-level jet (LLJ). The LLJ is primarily a nocturnal feature and typically occurs below 1000 m, with a peak wind often just a few hundreds of meters above the ground. The LLJ plays an important

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Keiichi Ishioka, Jitsuko Hasegawa, and Shigeo Yoden

1. Introduction Spontaneous zonal jet formation is a well-known significant feature in two-dimensional β -plane turbulence ( Rhines 1975 ; Vallis and Maltrud 1993 ). The formation itself is considered due to the upward cascade of energy that favors a zonal structure because of the β term. Vallis and Maltrud (1993) found asymmetry between eastward and westward jet profiles that emerged from turbulent states in the forced-dissipative numerical experiments. That is, eastward jets are

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Janni Yuval and Yohai Kaspi

1. Introduction The current understanding is that two types of jets exist in the atmosphere: a subtropical jet (STJ) and an eddy-driven jet (EDJ), also referred to in the literature as the subpolar jet. Two different mechanisms are responsible for the existence of these jets. The STJ is primarily driven by the advection of planetary angular momentum by the thermally direct Hadley circulation ( Held and Hou 1980 ), and eddies usually act to weaken this jet. On the other hand, the EDJ is driven

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Adam H. Monahan and John C. Fyfe

anomalies in the low and high latitudes (the black curve in Fig. 1 ). The associated time series is denoted the zonal index, and together with the dipole spatial pattern is typically interpreted as describing fluctuations in the central latitude of the eddy-driven jet (e.g., Robinson 1996 ; Feldstein and Lee 1998 ; DeWeaver and Nigam 2000 ; Lorenz and Hartmann 2001 ; Codron 2005 ; Wittman et al. 2005 ). In this study, the zonal index time series and its associated spatial pattern in zonal

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Yoshi N. Sasaki and Niklas Schneider

1. Introduction After leaving the coast of Japan around 35°N, the Kuroshio penetrates as a free jet into the North Pacific as the Kuroshio Extension (KE) and retains its sharp jet structure with associated fronts to the date line and beyond. The KE jet reaches its maximum speed on the order of 1 m s −1 at the surface and is accompanied by meridional potential vorticity (PV) gradients at the jet axis that are much larger than the planetary vorticity gradient ( Fig. 1 ). Fig . 1. A meridional

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Adam J. Clark, Christopher J. Schaffer, William A. Gallus Jr., and Kaj Johnson-O’Mara

1. Introduction A conceptual “four quadrant” model (4QM hereafter; e.g., Bluestein 1993 ; Rose et al. 2004 ) of upper-tropospheric linear jet streak circulations was first hypothesized by Namias and Clapp (1949) and later inferred through observations by Murray and Daniels (1953) . Using the quasigeostrophic momentum equation, it easily can be shown that the ageostrophic wind is directed perpendicular and to the left (in the Northern Hemisphere) of the acceleration of the wind. The

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Brian F. Farrell and Petros J. Ioannou

1. Introduction Coherent jets that are not forced at the jet scale are often observed in turbulent flows, with a familiar geophysical-scale example being the banded winds of the gaseous planets ( Ingersoll 1990 ; Vasavada and Showman 2005 ; Sánchez-Lavega et al. 2008 ). In the earth’s midlatitude troposphere, the polar-front jets are eddy driven ( Jeffreys 1933 ; Lee and Kim 2003 ). The earth’s equatorial stratosphere is characterized by the eddy-driven quasi-biennial oscillation (QBO) jet

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Lindsey N. Williams, Sukyoung Lee, and Seok-Woo Son

1. Introduction One peculiar feature in the atmosphere, which does not seem to have received much attention, is the fact that large-scale westerly jets, at times, take on a spiral form. An example of the spiral jet structure is shown in Fig. 1 , which displays the 275-hPa Southern Hemisphere (SH) zonal wind field, corresponding approximately to a 40-yr calendar mean of 27 April. A more precise description of the data and averaging procedure will be given in section 2 . Starting from the

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Ekaterina Ezhova, Claudia Cenedese, and Luca Brandt

1. Introduction This study focuses on the dynamics of an axisymmetric vertical turbulent jet in a stratified fluid. Vertical turbulent jets may serve as models of numerous flows both in nature and industry (see, e.g., Turner 1973 ; List 1982 ; Hunt 1994 ), including effluents from submerged wastewater outfall systems in the ocean (e.g., Jirka and Lee 1994 ), convective cloud flows in the atmosphere, pollutant discharge from industrial chimneys, and subglacial discharge from glaciers (e

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